Electric bicycles are seeing an increased uptake in Asia and Europe, but suffer from the fact that the battery forms a significant part of the weight of the bike. To charge the battery the user normally must plug in a conventional (typically 50-80 W) charger to the mains power supply. However, if the bike needs to be stored externally, such as at work or at a “park and ride” facility in a city, the charger needs weather proofing and isolation for safety for outdoors use. Further, it requires means to ensure it is safely secured from damage or accidental disconnect. The plugs used in such systems have a significant failure risk with use over time.
An alternative means of charging the battery is to remove it from the bike and take it to a charger inside a building. However, for the elderly (who can benefit the most from such powered assistance) the weight is prohibitive. Managed park and ride systems could potentially store an assortment of batteries and replace each battery when a bike is returned or “dropped off” from another station once the state of charge of a battery indicates that it requires charge/replacement, but there are significant problems with this model. Foremost of these is the need to have sufficient battery packs held on site, but additionally a range of charging stations suited to each available battery make and type will be required.
Any method of charging a battery without removing it from the vehicle should be safe and easy to use. One method which has previously been proposed is the use of an inductive power transfer (hereinafter referred to as IPT) system to transfer power from a charging station to a receiver mounted on the vehicle, for example at the end of a kick-stand. IPT can be used to provide a safe means of power transfer, as the danger associated with exposed live electrical contacts is eliminated. However, an IPT system should be efficient, and not create excessive electromagnetic interference. Stray magnetic fields can still be an issue, for example European field regulations of 6.25 uT have been suggested by ICNIRP.
The term “electric autocycle” is used herein to describe any two wheeled vehicle which is provided with an electric energy storage device. Such vehicles will usually, but not necessarily, be provided with an electric motor for the purposes of motive force, whether primary or supplementary, and includes electrically assisted bicycles and electric or hybrid scooters and motorcycles.